1. Field of the Invention
The present invention generally relates to a fuel evaporation gas transpiration prevention system for vehicles. More particularly, the present invention relates to a system for preventing the transpiration of fuel evaporation gas generated within a fuel supply system of an internal combustion engine of vehicles.
2. Description of Related Art
A system for preventing the transpiration of fuel evaporation gas generated within a fuel supply system of an internal combustion engine is disclosed in the Japanese Unexamined Patent Publication Laid-open No. 4-318268. According to the system disclosed in this publication, a fuel tank and a canister which adsorbs fuel evaporation gas communicate with each other with a single communication pipe, and within this communication pipe is disposed a two-way valve, while in the canister an atmospheric escape hole is provided.
In the system disclosed in above publication, fuel evaporation gas generated within the fuel tank during the refueling flows into the canister through the two-way valve and is adsorbed in an adsorbent within the canister. However, as the two-way valve does not open unless the pressure within the fuel tank increases to be larger than the pressure in the canister by a specified value, a part of the fuel evaporation gas generated within the fuel tank is released into the atmosphere through a bypass for refueling provided within the fuel tank until the pressure within the fuel tank increases to exceed a specified value.